Nuclear reactor shutdown caused by electrical issue

SEABROOK — An undetermined electrical issue caused coolant pumps at Seabrook Station nuclear power plant to turn off ahead of schedule early last week, forcing a reactor shutdown.

Kyle Stucker

SEABROOK — An undetermined electrical issue caused coolant pumps at Seabrook Station nuclear power plant to turn off ahead of schedule early last week, forcing a reactor shutdown.

Neil Sheehan, a public affairs officer for the Nuclear Regulatory Commission, said the reactor was operating at about 15 percent power when the electrical issue occurred on the secondary, non-nuclear side of the plant at about 12:26 a.m. Tuesday, April 1.

The reactor was scheduled to shut down early Tuesday morning as part of a planned routine refueling outage, and plant employees were in the process of implementing this when the coolant pumps stopped operating, according to Sheehan.

"They were very close to entering this refueling outage," Sheehan said. "This just accelerated their timeframe."

Seabrook Station Communications Manager Sarah Gebo said the process was accelerated by "about an hour." Gebo said the early shutdown didn't pose any cause for concern, as no radioactive releases occurred and all of the plant's "equipment performed as expected" during the efforts to bring the reactor to zero power.

NextEra Energy, owner of the plant, is still working to identify the problem that caused the early shutdown. Sheehan said the plant has "ample time" to go in and run diagnostics to determine and correct the issue, as the reactor was already scheduled to be offline for an undisclosed period of time starting Tuesday.

"We should know more about this sometime soon," Sheehan said. "It does take some time to run down the checklist and eliminate all of the possibilities."

Sheehan said "far less work" had to be done to safely cool the reactor Tuesday than if it had been running at or near 100 percent power. Even if the electrical system issue occurred while the plant's reactor was operating at a higher power, Sheehan said there wouldn't have been "any implications other than what (happened) with this one" because of various NextEra procedures and plans that address these situations.

"Even if the reactor protection system did not automatically shut down the reactor (as it did Tuesday), the operators are trained ...; to intervene and shut down the reactor themselves (when certain issues and conditions arise)," he said.

The Nuclear Regulatory Commission will oversee NextEra's assessment of the problem and work with the plant to develop corrective action, according to Sheehan.

It's unknown how long Seabrook Station's reactor will be shut down. Merchant plants like Seabrook Station don't disclose the length of their refueling outages, according to Gebo.

Refueling outages typically occur every 18 months to two years, and the last refueling outage at Seabrook Station occurred in 2012. Gebo said the station had been running for a station record 518 days before Tuesday's outage implementation began.

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